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Reopening of L-type calcium channels in human ventricular myocytes during applied epicardial action potentials

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Abstract Aims: 

Present study was performed to compare the dynamics of human L-type calcium current (ICa,L) flowing during rectangular voltage pulses, voltage ramps, and action potentials (APs) recorded from epicardiac and endocardiac canine ventricular cells. Methods: 

ICa,L was recorded in single myocytes isolated from undiseased human hearts using the whole cell voltage clamp technique. Results: 

The decay of ICa,L was monotonic when using rectangular pulses or endocardial APs as voltage commands, whereas the current became double-peaked (displaying a second rise and fall) during epicardial (EPI) APs or voltage ramps used to mimic EPI APs. These ICa,L profiles were associated with single-hooked and double-hooked phase-plane trajectories, respectively. No sustained current was observed during the AP commands. Kinetics of deactivation and recovery from inactivation of human ICa,L were determined using twin-pulse voltage protocols and voltage ramps, and the results were similar to those obtained previously in canine cells under identical experimental conditions. Conclusions: 

ICa,L can inactivate partially before and deactivate during the phase-1 repolarization of the epicardiac AP, and reopening of these channels seems to be associated with formation of the dome.

Keywords: action potential; calcium current; human myocytes; regional differences; voltage clamp

Document Type: Research Article


Affiliations: 1:  Department of Physiology, University Medical School of Debrecen, Debrecen, Hungary 2:  Department of Pharmacology and Pharmacotherapy, University of Szeged, Szeged, Hungary

Publication date: January 1, 2004


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